Email Queue

Hello, I've been trying to isolate an issue with our submission forms not being delivered. I see our email queue has been backed up for a couple days now and in the waiting "waiting" status. The error message on each record is "The server committed a protocol violation the server response was:" and nothing else. To my knowledge nothing has changed within our configuration (back or frontend).

I also tried to send a test email from the "Send Email" tab and that is stuck in the queue. If I try to select it from the list and attempt to resend, it fails as well.